Influence of Sn4+ substitution for Si4+ on the microwave dielectric properties of Mg₂Al₄Si5−xSnxO18 ceramics

The Mg 2 Al 4 [Formula: see text]Sn x [Formula: see text] ([Formula: see text]) ceramics were successfully synthesized via the solid-state reaction method. The XRD results show that the main phase of the ceramics is Mg 2 Al 4 Si 5 [Formula: see text]. When [Formula: see text], there is a second phase of Al 2 SiO 5 . With the increase of x, the content of [Formula: see text] gradually increased, the Al 2 SiO 5 phase disappeared, and the SnO 2 and MgAl 2 O 4 phases appeared. In addition, the cell volume of the ceramic changes with the increase of x, which indicates that partial [Formula: see text] successfully enters the lattice with ion substitution and lattice distortion. The relative density and [Formula: see text] are highly correlated. The quality factor (Qf) is not only affected by the relative density but also by the symmetry of the [Si 4 Al 2 ] ring. The bond strength as an evaluation of the stability of the crystal structure determines the magnitude of [Formula: see text]. Good microwave dielectric properties were achieved for samples at [Formula: see text] with sintering at 1400 ∘ C: [Formula: see text], [Formula: see text][Formula: see text]GHz and [Formula: see text][Formula: see text]ppm/ ∘ C, demonstrating that Mg 2 Al 4 [Formula: see text][Formula: see text][Formula: see text] ceramics are an ideal candidate for microwave electronics.